1. Field of the Invention
The present invention relates to a method of fabricating semiconductor devices. More particularly, the present invention relates to a method of forming a bonding pad opening.
2. Description of Related Art
After semiconductor devices are completely fabricated, an uppermost metal layer is usually patterned to form a bonding pad, and a passivation layer is covered thereon. After that, a bonding pad opening is formed in the passivation layer, and subsequent package processes are then implemented. Nevertheless, pittings arisen from the corrosion of metals are frequently generated on upper surfaces of the semiconductor devices before the package processes are performed. In addition, during an etching process, polymer by-products formed at sidewalls of the bonding pad opening may not be completely removed in some cases. The residual polymers are likely to contaminate a testing apparatus in the subsequent package processes. Besides, corrosive gases may also be released due to a rising temperature during the operation of integrated circuits. Accordingly, in order to ensure reliability, the removal of the polymer by-products generated during the etching process has always been an important research topic.
In U.S. Pat. No. 5,930,664, a method for preventing corrosion of aluminum bonding pads after a passivation layer/an anti-reflection coating (ARC) layer etching is provided. Said patent discloses a formation of polymers in the last step of etching the passivation layer, so as to protect the aluminum bonding pads from being corroded because of an exposure to moisture. However, an important issue of removing the residual polymers remains unresolved in said patent.
In U.S. Pat. No. 6,006,764, a method of stripping photoresist from aluminum bonding pads that prevent corrosion is disclosed. In the patent, after a passivation layer is etched, a wet cleaning process is implemented to clean a wafer, and then the wafer is moved to a reactive ion etching station, so as to remove residual chlorine with use of plasma generated by a fluorine-containing gas. Finally, the wafer is moved to a photoresist asher for performing an oxygen ashing treatment. Nevertheless, the wafer of said patent is first cleaned through the wet cleaning process, and thereby a significant amount of the photoresist may remain if a solution with extremely large polarity is not employed, resulting in contamination of the station in subsequent processes.
In U.S. Pat. No. 6,221,752, a method of mending erosion of a bonding pad is provided. In the patent, a passivation layer is completely etched, and an eroded part of the bonding pad is then removed. Thereafter, an oxide layer is formed subsequently on a clean surface exposed by the removed part of the bonding pad. However, said patent is actually directed to a repairing method rather than a preventive measure.
In U.S. Pat. No. 6,355,576, a method for cleaning integrated circuit bonding pads is provided. In the patent, plasma having CF4 and water vapor combination is adopted to treat the bonding pads after a passivation layer is completely etched. The plasma having the water vapor is able to evaporate fluorine residue on the bonding pads, while the CF4 plasma is capable of removing polymers to a great extent. Next, photoresist is ashed with use of oxygen plasma, and a wet cleaning process is then performed. However, the issue regarding the fluoridized bonding pads remains unsolved in the patent.
In U.S. Pat. No. 5,172,212, a semiconductor device is provided with an improved bonding pad. In said patent, after a bonding pad opening is formed but before a photoresist layer is removed, a metal barrier layer is formed on the bonding pad exposed by the bonding pad opening. Next, the photoresist layer is removed, and a wire-bonding process is then implemented. However, said patent does not propose any method of cleaning the bonding pad. Moreover, as the metal barrier layer is sputtered, the high out gassing level of photoresist and photoresist scumming arisen from the sputtering process may result in contamination. On the other hand, when the metal layer serving as the bonding pad is patterned, no ARC layer is formed on the metal layer. Accordingly, accuracy of a photolithography process may be affected, giving rise to deviations of critical dimensions.